1. Field of the Invention
The invention relates to an electricity charging system and, more particularly, to an electricity charging system that clearly shows information regarding the amount of stored electricity of a storage battery that is being charged.
2. Description of Related Art
When a storage battery is being charged, information that is important to a user of the storage battery is information regarding how long it is before the charging ends, information regarding how much electricity has been stored at the present time point, etc.
Japanese Patent Application Publication No. 03-242574 (JP-A-03-242574) discloses a technology that displays an amount of electricity remaining in the storage battery by using as an index the amount of electricity stored into the storage battery per unit time from an empty state to a fully charged state.
Besides, Japanese Patent Application Publication No. 2003-319563 (JP-A-2003-319563) discloses an electronic appliance that changes the charging mode during the charging of a battery pack or stops the charging by transmitting, by communication, information regarding charging electricity between the battery pack and an electronic appliance that has an electrical charging function.
However, in the foregoing technology described in Japanese Patent Application Publication No. 03-242574 (JP-A-03-242574), since the amount of electricity stored per unit time is used as an index, there is a problem of the index being unable to show whether the storage battery is relatively close to the empty state or relatively close to the fully charged state.
In the technology described in Japanese Patent Application Publication No. 2003-319563 (JP-A-2003-319563), a facility for communicating information is needed in addition to the facility for sending electric power from the charging side to the storage battery. For the communication, compatible communication protocols need to be adopted at the charging side and the storage battery side, so that the compatibility with other types of charging appliances is lost. Besides, in the case where the charging side is provided as a facility that is installed in a building and the storage battery is mounted in a vehicle, there is a possibility of the facility for the communication being wasted by the vehicle user's replacement purchase.
In any case, the foregoing technologies have a problem of requiring the two sides to have communication facilities for exchanging information regarding the amount of electricity stored in the storage battery.